FIELD OF THE INVENTION
This invention relates to tunable electronic musical instruments of the keyboard type and particularly to the capability of producing scales having 24 or more pitches in each octave or producing, simultaneously, at least two of the many twelve note scales needed for teaching, research, performance and composition.
In contemporary music composition and performance the use of microtonal scales (scales having more than twelve notes per octave) is of increasing importance. There are various instruments on the market, such as the synthesizers, which can produce such scales, but all of them have some of all of the following disadvantages. Each pitch must be established, then recorded, the next pitch established and recorded, and so on in sequence. Pitches are not drift free, thus constant rechecking of pitch is required. Only the recording becomes a "performance" as it is virtually impossible to perform "live" on such instruments. Also, they are not playable by normal keyboard techniques, and require much specialized training by the potential user.
In the past, research and teaching in music theory of such subjects as harmonics and intervals has usually involved the use of laboratory-type setups including a multiplicity of oscillators, amplifiers, speakers and such. Accuracy was limited and difficult to prove. Phonograph records were often used in the classroom to avoid the laboratory setup but this technique restricted the instructor's scope in teaching and was also limited in accuracy. Again, in music history, records were often resorted to in order to study the scales of intricate, expensive or even extinct authentic instruments. Thus, the teaching of music history has tended to have a dull textbook approach. And this problem is not new. Marin Mersenne, seventeenth century authority on tuning, in his "Harmonie Universelle" and other works, provides descriptions of many scales with more than twelve notes per octave and sketches of complicated key-boards on which to play them. Few if any of them were practical designs, and of course, each instrument would have been difficult to tune and impossible to tune accurately.
A leading musicologist of the present day, J. Murray Barbour, in his "Tuning and Temperament" lists 179 different historical scales from the Western world alone, and describes many of the interesting attempts to make these scales available on an actual instrument. As an example, Georg Frederick Handel played on a number of English organs with split keys which had been designed in an attempt to obtain improved tuning. Almost without exception these instruments were still limited to one particular scale.
In ethnomusicology, volumes have been and are being written on the music of various contemporary cultures. In some cultures the musical scales vary from village to village. Reproduction of these was very difficult unless the authentic instruments for each village were available.
The study of the physics of sound and music can be greatly facilitated by the capability of producing on a keyboard instrument two or more tones with exactly controllable pitch or phase difference between them. The study of "monaural" beats is a vital part of acoustic research but is also necessary in music training for learning to tune instruments such as the violin, to play "in tune" on instruments such as the clarinet, and to train the young musician's ear to hear perfect intervals. A new field of research is that of "binaural" beats, where two signals are fed to a subject's ears with absolutely no electronic or acoustic mixing of the signals. In the past, such research has used two cellos in separate rooms, with separate microphones and amplifiers, each fed to one headphone. (See "Some Aspects of Binaural Sound," Charles J. Hirsch, RCA, IEEE Spectrum, Feb. 1967, pages 80-85.) Even when oscillators were substituted for the two cellos the problems of exact control and measurement were almost insurmountable. (See "Auditory Beats in the Brain," Gerald Oster, Scientific American, Oct. 1973, pages 94-102, and "Limits for the Detection of Binaural Beats," D. Perrott and M. Nelson, The Journal of the Acoustical Society of America, Dec. 1969, pages 1,477-1,481.)
In the field of music history many important scales have had other than 12 notes to an octave, varying from the Greek tetrachord with 4 notes to at least 31 notes in the Meantone temperaments. In ethnomusicology, many scales of recent or current cultures involve more than 12 notes to the octave. Contemporary musicians are composing in many of these scales and in others such as quarter tone, third tone, and various microtonal scales such as those with 13, 17, 23 or 53 notes per octave. There has been a widespread and previously unmet demand for an instrument with such capabilities.
Although many devices and systems have been devised to solve one or more of the above problems most of them lack the accuracy and simplicity which make the present invention desirable. All of them lack the reproducibility and real time accessibility which is vital to much teaching and research.
Likewise, many systems of notation have been devised in the attempt to provide for these many scales, but no single system was devised that would satisfy all requirements.